From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750843AbVHMAsK (ORCPT ); Fri, 12 Aug 2005 20:48:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751317AbVHMAsJ (ORCPT ); Fri, 12 Aug 2005 20:48:09 -0400 Received: from gateway-1237.mvista.com ([12.44.186.158]:14587 "EHLO av.mvista.com") by vger.kernel.org with ESMTP id S1750836AbVHMAsI (ORCPT ); Fri, 12 Aug 2005 20:48:08 -0400 Message-ID: <42FD42C1.6040009@mvista.com> Date: Fri, 12 Aug 2005 17:45:53 -0700 From: George Anzinger Reply-To: george@mvista.com Organization: MontaVista Software User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050323 Fedora/1.7.6-1.3.2 X-Accept-Language: en-us, en MIME-Version: 1.0 To: lkml , Andrew Morton Subject: [PATCH] eliminte NMI entry/ exit code Content-Type: multipart/mixed; boundary="------------000805030702000009090001" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------000805030702000009090001 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit The NMI entry and exit code fiddles with bits in the preempt count. If an NMI happens while some other code is doing the same, bits will be lost. This patch removes this modify code from the NMI path till we can come up with something better. -- George Anzinger george@mvista.com HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/ --------------000805030702000009090001 Content-Type: text/plain; name="fix-nmi-enter.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="fix-nmi-enter.patch" Source: MontaVista Software, Inc. George Anzinger Type: Defect Fix Description: Modifying a word from NMI code runs the very real risk of loosing either then new or the old bits. Remember, we can not prevent an NMI interrupt from ANYWHERE, inparticular between the read and the write of a read modify write sequence. This patch removes the update of the preempt count from the NMI path. Signed-off-by: George Anzinger hardirq.h | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) Index: linux-2.6.13-rc/include/linux/hardirq.h =================================================================== --- linux-2.6.13-rc.orig/include/linux/hardirq.h +++ linux-2.6.13-rc/include/linux/hardirq.h @@ -98,9 +98,12 @@ extern void synchronize_irq(unsigned int #else # define synchronize_irq(irq) barrier() #endif - -#define nmi_enter() irq_enter() -#define nmi_exit() sub_preempt_count(HARDIRQ_OFFSET) +/* + * Re think these. NMI _must_not_ share data words with non-nmi code + * Meanwhile, just do a no-op. + */ +#define nmi_enter() /* irq_enter() */ +#define nmi_exit() /* sub_preempt_count(HARDIRQ_OFFSET) */ #ifndef CONFIG_VIRT_CPU_ACCOUNTING static inline void account_user_vtime(struct task_struct *tsk) --------------000805030702000009090001--